Bowser is Mario's archnemesis. He is the leader and most powerful of the turtle-like Koopa race. Although Bowser has joined forces with Mario in a few games, he is considered a "bad guy" due to his ambition to kidnap and dethrone Princess Peach and conquer the Mushroom Kingdom.

Though their origins are unknown, Bowser has eight children; the seven Koopalings and Bowser Jr.

Bowser, or King Koopa, is perhaps most famous for his repeated kidnappings of Princess Peach. The reason for these kidnappings is often part of his plan to take over the Mushroom Kingdom.

He has several types of troops under his command, including Koopas, Goombas, and Piranha Plants.

Bowser's appearance has been tweaked several times throughout the series, but most of basic overall look has been consistent. He looks something like a cross between a turtle and a dragon. He is bipedal and able to walk around on two legs. Both his feet and his hands have large claws. He is noticably larger than all the other characters. He is mostly yellow with a green shell. Several large spikes are located both on his tail and on his shell. He sports a tuft of red hair on top of his head. Although his abilities vary from game to game, he is able to breathe fire in most of them.